1. FIELD OF THE INVENTION
The invention relates to a running tool for effecting the run-in of a liner running tool and a depending liner in the bore of the casing of a subterranean well, and particularly to a running tool which is normally hydraulically released from the liner hanger.
2. SUMMARY OF THE PRIOR ART
It has been a common practice in the oil and gas well industry to run casings part way into a well bore and then suspend a smaller diameter liner string from the bottom portions of the casing to traverse the remaining portions of the well bore. This necessarily requires a liner hanger which can be appropriately engaged with the casing wall to suspend the depending liner string and which normally requires a running tool to effect the insertion of the liner hanger and the depending liner string.
It is highly desirable that the running tool be capable of effecting rotation of the liner hanger in either direction in order to free the liner string from any obstacles that it may encounter in the course of its passage through the bore of the casing and the bore of the uncased portion of the well. Many liner running tools have been proposed wherein the rotation of the running tool in a particular direction, accompanied by either a tension or a compression force effects the release of the running tool from the hanger and premature releases have been all too common in the industry.
Additionally, running tools for liner hangers have been proposed wherein the release of the liner is accomplished by a hydraulically actuated mechanism, but the failure of a seal or a valve involved in such mechanism completely prevents the release of the running tool, requiring that the running tool liner hanger and depending liner string be removed from the well for the necessary repairs or adjustments.
The prior art has not provided a liner running tool which is capable of imparting rotation in either direction to the liner hanger for run-in purposes and which will impart such rotation when under either a compressive or a tensile stress without effecting the premature release of the running tool from the liner hanger. Additionally, the prior art has not provided a hydraulic release mechanism for a liner hanger which can, in an emergency, be mechanically actuated to effect the complete release of the running tool from the liner hanger.